This invention relates generally to the field of structures and, more specifically, to a system and method for evaluating a structure.
The integrity of many structures, such as aircraft parts, which can be composed of metal, plastic, or composite, can be degraded by the presence of defects as well as the effects of age and wear. Defects can include cracks, delaminations, voids, or corrosion and are a prelude to structural failure. Thus, early detection of defects is a significant advantage. Unfortunately, defects can be buried deep within a structure, hidden in complex structures, or in their incipiency, making them difficult to detect without highly intrusive measures, which can damage the structure.
Currently, active source thermography is used to detect such defects in structures. In this process, a strong thermal pulse is directed at the outside surface of a structure, and the resulting temporal evolution of the surface heat signature is measured. The presence, size, and types of defects can be determined by analyzing the evolution of the surface thermal signature with knowledge of the physical thermal properties of the materials present because defects within the structure perturb the flow of heat compared with an idealized structure. The thermal pulse for this process is generally provided by a flash-lamp, and the surface temperatures are mapped using time resolved infrared imaging.
This technique, however, only works well for detecting defects in the flat, two dimensional surface of the structure. Thus, for deeply buried defects, complex structures, or incipient defects, an externally applied thermal pulse does not provide sufficient sensitivity. Better methods are needed, therefore, to detect defects buried in structures, in complex structures, or in their incipiency, before the onset of structural failure.
In accordance with the present invention, a method and system for evaluating a structure are provided that substantially eliminate or reduce at least some of the disadvantages and problems associated with previously developed systems and methods.
A system for evaluating a structure is disclosed. In this system, the structure to be evaluated has a predetermined baseline thermal signature. The system includes a thermal source located at least partially inside the structure. The thermal source is operable to generate a predetermined amount of heat, which heats the structure. The system also includes a detection device that is operable to determine the temperature at various points of the structure. The system further includes a computer that is coupled to the detection device. The computer is operable to generate a thermal signature of the structure based on the temperature at the various points of the structure. The generated thermal signature is compared to the baseline thermal signature to determine whether anomalies exist in the structure.
A method for evaluating a structure is also disclosed. The method includes five steps. Step one calls for locating a thermal source at least partially inside a structure to be evaluated. Step two requires generating a predetermined amount of heat with the thermal source. The third step calls for determining the temperature at various points of the structure. In step four, the method calls for generating a thermal signature of the structure based on the temperature at the various points of the structure. The final step of the method calls for comparing the generated thermal signature of the structure to a predetermined baseline thermal signature of the structure.
A technical advantage of the present invention is that heat from the thermal source is transferred to the inside of the structure. Thus, defects that are buried deep within the structure or hidden from the outside by other components of the structure can be heated. Therefore, because these defects affect the thermal signature of the structure, analyzing the thermal signature of the structure due to this type of heating enhances the probabilities of detecting a defect. Another technical advantage is that the amount of heat transferred to the structure by the thermal source can be accurately controlled. This ability provides for a more accurate determination of the defects in the structure, compared to an externally applied thermal pulse. In addition, this ability allows incipient defects to be identified. Moreover, accurate control of the heat transferred to the structure helps to ensure that the structure is not damaged by the evaluation. Other technical features and advantages will be readily apparent to those skilled in the art.